Display module and method for coating the same

ABSTRACT

The present disclosure provides a display module and a method for coating the same, which can prevent and/or reduce the occurrence of black seam between display modules that are arranged adjacent to each other. According to an example aspect of the present disclosure, a display module includes a printed circuit board; a plurality of luminous elements arranged at predetermined intervals on the printed circuit board; and a coating layer comprising a coating disposed between the respective luminous elements, disposed around side surfaces of the respective luminous elements positioned at an outermost, and formed to have a height that is substantially equal to a height of the side surfaces of the luminous elements, the coating being configured to block side light of the respective luminous elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. § 119to Korean Patent Application No. 10-2016-0072740 filed on Jun. 10, 2016in the Korean Intellectual Property Office, the disclosure of which isincorporated by reference herein in its entirety.

BACKGROUND

Field

The present disclosure relates generally to a display module and amethod for coating the same using a coating jig device, and for example,to a display module having a coating layer formed thereon to blocksidelight of a plurality of luminous elements that are arranged on aprinted circuit board, and a method for coating the display module usinga coating jig device that guides edges of the printed circuit board thecoating layer to surround side portions of the respective luminouselements.

Description of Related Art

In general, an LED display includes a plurality of LED elements mountedthereon at predetermined intervals. Such an LED display is the nextgeneration display system that substitutes for a typical liquid crystaltype display, and has the advantages of high color representation andhigh luminance picture quality. An LED display having specificresolution is composed of unit modules (hereinafter referred to as“display modules”), and several display modules are connectedly attachedin the form of a matrix to form a single display.

However, due to a machining error of the sizes of printed circuit boardsof respective display modules and a difference in the degree of closecontact between the respective display modules that occurs when therespective display modules are installed on a frame in the form of aseries array, a mechanical gap may occur between the display modules tocause a black seam to be visually recognized. Accordingly, in the caseof connecting the display modules in the related art in the form of amatrix, it is required to put a great deal of effort in order to preventthe machining error from occurring, and it costs a lot in managing themachining error of the printed circuit board.

In addition, a plurality of LED elements mounted on a display module aredisposed with the same intervals. When making a multi-vision byconnecting the plurality of display modules, there may be a problem ofwhite seam that luminance between display modules is brighter thanluminance between LED elements mounted on a single display module. Thereason why white seam occurs is as shown below. When making a printedcircuit board of a display module, if a margin (a distance from theoutermost LED element to an edge of the printed circuit board) of theprinted circuit board is formed to be shorter than a predetermineddistance, when a printed circuit board having a short margin(hereinafter ‘a first substrate’) is connected to a printed circuitboard of another display module (hereinafter ‘a second substrate’),intervals between the LED element arranged at the outermost of the firstsubstrate and the LED element arranged at the outermost of the secondsubstrate are narrower than the intervals among a plurality of LEDelements mounted on a single display module. Due to the above, totallight quantity between the LED element arranged at the outermost of thefirst substrate and the LED element arranged at the outermost of thesecond substrate is larger than total luminance between two columns of aplurality of LED elements mounted on the single display module andaccordingly, a phenomenon that a portion between the first substrate andthe second substrate that are arranged adjacent to each other looksbrighter, i.e., white seam, occurs.

Further, the display module in the related art is provided with an anodeelectrode and a cathode electrode that are exposed to an outside. Theseelectrodes may cause the LED elements to be burnt when an electrostaticdischarge is projected onto the display module. Due to this, there is ahigh possibility that a control circuit that is electrically connectedto the respective electrodes is damaged. In this case, the electrostaticimmunity of the LED element becomes 0 to 2 KV and the electrostaticimmunity of the control circuit element connected to the LED elementbecomes about 1 to 4 KV, which do not satisfy the international standardthat corresponds to the electrostatic immunity of 8 KV. Accordingly, itis general to cope with overvoltage by designing a TVS (TransientVoltage Suppressor) diode between the cathode electrode and ground.However, in this case, the manufacturing cost of the display module isincreased, and the complexity of the circuit design is increased.

As another means for solving the above-described problem, a transparentcoating solvent is spread on one surface of the display module, and sucha coating process is mainly performed through spraying, potting, andparylene deposition.

However, according to the coating technology in the related art, atransparent coating solvent is attached to an upper surface of the LEDelement. In the case where the transparent coating layer is formed onthe upper surface of the LED element, picture quality may deteriorateand luminous color may be shifted. Accordingly, the transparent coatinglayer that is formed on the upper surface of the LED element has lightrefractive index and permeability that are different from those of anLED molding surface, and thus unintended picture quality deteriorationand color change may occur. In order to solve this problem, in order toblock unintended light that is emitted from four side surfaces of theLED element, a technology to mount and mold the LED element in an opaquepackage has been proposed. However, such a technology in the related arthas the problem that it is very difficult to implement the technology ina display module that uses micro LED elements that are equal to orsmaller than 1 mm×1 mm.

Further, Japanese Registered Patent No. 3875768 (published on Feb. 26,1999) discloses a configuration in which a filler is coated on a displaymodule having a plurality of LED elements. In this case, the displaymodule is provided with a rear cover that simultaneously surrounds therear surface and the side surface of a printed circuit board so as toprevent the filler that is coated on one surface of the printed circuitboard from being spilled. Such display modules are connected to oneanother in the form of a matrix to be used in a large-sized electronicsignboard that is mainly installed outdoors.

Accordingly, such a display module uses LED elements having relativelylarge size and also has a large pitch between LEDs, and thus there is nodifficulty in coating the filler between the respective LEDs.

However, as described above, such a coating technology has the problemthat it is unable to be adopted in coating the coating solvent betweenthe micro LED elements having the size of 1 mm×1 mm. Further, since thedisplay module should always be provided with a rear cover, the sidesurfaces of the respective rear covers of adjacent modules come incontact with each other, and in this case, the black seam may be seen.

SUMMARY

Example embodiments of the present disclosure are provided to addressthe above disadvantages and other disadvantages not described above, andprovide a display module and a method for coating the same, which canprevent and/or reduce the occurrence of white seam that is caused byluminous elements arranged at the outermost portions of display modulesthat are arranged adjacent to each other.

Example embodiments of the present disclosure provide a display moduleand a method for coating the same, which can prevent and/or reduce theoccurrence of black seam between display modules that are arrangedadjacent to each other.

According to an example aspect of the present disclosure, a displaymodule includes a printed circuit board; a plurality of luminouselements arranged at predetermined intervals on the printed circuitboard; and a coating layer disposed between the respective luminouselements and between the luminous elements positioned at an outermostportion of the display module and the edge of the printed circuit board,the coating layer being configured to block side light of the respectiveluminous elements.

The coating layer may be formed with a height that is substantiallyequal to a height of the side surface of the luminous element to blocklight that is emitted to the side surface of the luminous element.

A pitch between the respective luminous elements may be set to a rangeof 0.3 to 2 mm. The size (width×length×height) of the luminous elementmay be defined that a range of the width×length is 0.5 mm×0.5 mm to 3mm×3 mm, and a range of the height is 0.5 mm to 1.2 mm.

The coating layer may cover electrodes of the respective luminouselements. The coating layer may comprise an opaque non-conductivematerial. For example, the coating layer may comprise silicon, acrylicresin, or epoxy resin. Viscosity of a coating solvent that forms thecoating layer may be in a range of 1000 to 10000 p(poise), and morepreferably 2000 to 9000 p(poise).

According to another example aspect of the present disclosure, a displaymodule includes a printed circuit board; a plurality of luminouselements mounted at intervals on the printed circuit board; and opaquecoating layer formed on the printed circuit board to surround sideportions of the respective luminous elements, the opaque coating layerhaving an edge portion that forms an outer portion of the opaque coatinglayer, and the edge portion having a projection portion that projectsfurther than an edge of the printed circuit board.

The edge portion of the opaque coating layer may come in contact with anedge portion of an opaque coating layer of another display modulearranged adjacent to the display module. In this case, the opaquecoating layer may have an elastic force wherein the adjacent coatinglayers come in close contact with each other without forming a spacebetween them.

The edge portion of the opaque coating layer may project graduallyslantingly in a direction away from the printed circuit board. The edgeportion of the opaque coating layer may be slanting to form an acuteangle with a virtual straight line that vertically extends from the edgeof the printed circuit board. The edge portion of the opaque coatinglayer may have a planar or curved side surface.

According to still another example aspect of the present disclosure, amethod for coating a display module includes preparing a display modulein which a plurality of luminous elements are mounted at intervals on aprinted circuit board; arranging a jig along an edge portion of theprinted circuit board; forming a coating layer that surrounds sideportions of the respective luminous elements by discharging an opaquecoating solvent between the respective luminous elements and between therespective luminous elements positioned at an outermost portion of thedisplay module and the edge of the printed circuit board; and separatingthe jig from the printed circuit board.

The forming the coating layer may discharge the opaque coating solventat a height so that the opaque coating solvent surrounds a remainingportion excluding upper surfaces of the respective luminous elements.

The forming the coating layer may fill up to a region that projectsfurther than an edge of the printed circuit board with the opaquecoating solvent by means of a slanting surface that is slanting towardan outside of the jig in a direction toward an upper side of the jig.

The method may further include grinding an outside of the coating layerthat is formed as the opaque coating solvent is cured.

The opaque coating solvent that is discharged through a nozzle at theforming the coating layer may be controlled by a piezo valve or apneumatic valve.

The forming the coating layer may discharge the opaque coating solventthrough the nozzle having a diameter in a range of 50 to 300 μm.

Additional and/or other aspects and advantages of the disclosure will beset forth in part in the description which follows and, in part, will beapparent from the description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the present disclosure will be moreapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, in which like reference numerals referto like elements, and wherein:

FIG. 1 is a diagram illustrating an example single display device thatis formed by arranging display modules in the form of a matrix accordingto an example embodiment of the present disclosure;

FIG. 2 is a diagram illustrating any one of a plurality of exampledisplay modules as illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of an example display module takenalong line as indicated in FIG. 2;

FIG. 4 is a perspective view of an example display module illustrating apart IV as indicated in FIG. 2;

FIG. 5 is a cross-sectional view of a part V as indicated in FIG. 1illustrating a state where edges of coating layers of adjacent displaymodules come in contact with each other;

FIG. 6 is a flowchart illustrating an example process of forming acoating layer on a display module according to an example embodiment ofthe present disclosure;

FIG. 7 is a plan view illustrating an example state where a jig is setalong edges of four sides of a printed circuit board before a coatinglayer is formed;

FIG. 8 is a cross-sectional view of an example display module and a jigtaken along line VIII-VIII as indicated in FIG. 7;

FIG. 9 is a diagram illustrating an example discharge device fordischarging a coating solvent that is filled between respective luminouselements of a display module and between the outermost luminous elementand a jig;

FIGS. 10A and 10B are diagrams illustrating an example process ofdischarging a coating solvent through an operation of a piezo valve thatis provided in an example discharge device;

FIG. 11 is a cross-sectional view illustrating a state where filling ofa coating solvent between respective luminous elements of a displaymodule and between the outermost luminous element and a jig iscompleted;

FIG. 12 is a cross-sectional view illustrating another example of a jigthat guides filling of a coating solvent; and

FIGS. 13A, 13B, 13C and 13D are cross-sectional views illustratingvarious example cross-sectional shapes of an edge portion of a coatinglayer.

DETAILED DESCRIPTION

Hereinafter, various example embodiments of the present disclosure willbe described with reference to the accompanying drawings. However, itshould be understood that the present disclosure is not limited to thevarious example embodiments described hereinafter, but may includevarious modifications, equivalents, and/or alternatives of theembodiments of the present disclosure. In relation to explanation of thedrawings, similar drawing reference numerals may be used for similarconstituent elements.

In the description, the dimensions, which correspond to a size(w1×w2×h1) of a luminous element, a pitch g1 between respective luminouselements, a height h3 of a coating layer, a width w3 of an edge portionof a coating layer, and a width w4 of an edge portion of a printedcircuit board, are exemplified to indicate that the size of the luminouselements provided in the display module according to an exampleembodiment of the present disclosure is small-sized or ultrasmall-sized.In addition, “an edge portion” mentioned in this disclosure is a portionwhich forms an outer portion of a coating layer and indicates a portionfrom a side of a luminous element to an edge of a printed circuit board(see ‘w4’ illustrated in FIG. 3). Further, ‘a projection portion’indicates a portion which is extended from the edge portion and furtherprotrudes than an edge of a printed circuit board (see 45′ illustratedin FIG. 3).

The terms used in the description are used to merely describe an exampleembodiment, but may not intend to limit the scope of other embodiments.A singular expression may include a plural expression unless speciallydescribed. All terms (including technical and scientific terms) used inthe description could be used as meanings commonly understood by thoseordinary skilled in the art to which the present disclosure belongs. Theterms that are used in the present disclosure and are defined in ageneral dictionary may be used as meanings that are identical or similarto the meanings of the terms from the context of the related art, andthey are not interpreted ideally or excessively unless they have beenclearly and specially defined. According to circumstances, even theterms that are defined in the present disclosure should not beinterpreted to exclude the embodiments of the present disclosure.

Hereinafter, with reference to the accompanying drawings, theconfiguration of a display module according to an example embodiment ofthe present disclosure and a method for forming a coating layer on adisplay module using a jig will be described in greater detail.

FIG. 1 is a diagram illustrating an example single display device thatis formed by arranging display modules in the form of a matrix accordingto an example embodiment of the present disclosure.

Referring to FIG. 1, display modules 100 according to an exampleembodiment of the present disclosure may be arranged to be mutuallyconnected in the form of a matrix to form a single display device 10. Inthis example, the single display device 10 may include a driver (notillustrated) for driving the respective display modules 100, acontroller (not illustrated) for controlling the driver, a power supply(not illustrated), and a plurality of wirings (not illustrated) forapplying various kinds of signals.

FIG. 2 is a diagram illustrating an example of any one of a plurality ofexample display modules as illustrated in FIG. 1, and FIG. 3 is across-sectional view of an example display module taken along line asindicated in FIG. 2. FIG. 4 is a perspective view of an example displaymodule illustrating a part IV as indicated in FIG. 2.

Referring to FIG. 2, the display module 100 includes a printed circuitboard 110, a plurality of luminous elements 130 arranged atpredetermined intervals on one surface 110 a (see FIG. 3) of the printedcircuit board 110, and a coating layer 150 that is coated on the onesurface 110 a of the printed circuit board 110 on which the plurality ofluminous elements 130 are mounted.

The printed circuit board 110 may be in a substantially rectangularshape so that it can be easily arranged in the form of a matrix when thedisplay module 100 is connected to an adjacent display module 100, butis not limited to a rectangular shape.

However, the shape of the printed circuit board 110 is not limitedthereto, and the printed circuit board 110 may have any shape so far asit can be easily connected to an adjacent printed circuit board 110.Further, the thickness t (see FIG. 3) of the printed circuit board maybe greater than the height h1 of the luminous element 130.

In this example embodiment, the printed circuit board 110 is illustratedas having a planar shape, but is not limited thereto. The printedcircuit board 110 may have a curved surface having a predeterminedcurvature. In this example, a single curved display device may be formedby connecting display modules 100 to one another in the form of amatrix.

Referring to FIGS. 2 and 3, a plurality of luminous elements 130 may bearranged at predetermined intervals on one surface 110 a of the printedcircuit board 110 in the form of a matrix. Each luminous element 130may, for example, be substantially in a cuboidal shape, and may be asmall-sized or ultrasmall-sized LED having, for example, a size (width(w1)×length (w2)×height (h1)) that is equal to or smaller than 1 mm×1mm×0.7 mm. In this case, the size of (width×length) may be selected in arange of 0.5 mm×0.5 mm to 3 mm×3 mm, and height may be selected in arange of 0.5 mm to 1.2 mm.

The luminous element 130 may emit light through four side surfaces 131and an upper surface thereof 133, and an anode electrode 135 and acathode electrode 137 may be provided on a bottom surface thereof. Theanode electrode 135 and the cathode electrode 137 may be soldered ontopatterns 115 and 117, respectively, formed on the printed circuit board110. In this example, the height h2 that is measured from one surface ofthe printed circuit board 110 to upper ends of the respective electrodes135 and 137 may be 0.1 mm or about 0.1 mm.

Further, as the size of the luminous element 130 is small or ultrasmall,the pitch g1 of the luminous element 130 may be quite narrow, forexample, the pitch may be set to be equal to or smaller than 0.5 mm orabout 0.5 mm Preferably, the pitch g1 of the luminous element 130 may beset within a predetermined range (e.g., 0.3 to 2 mm) in accordance withresolution to be implemented by the single display device 10 (see FIG.1).

Referring to FIG. 2, the coating layer 150 that is made, for example, ofan opaque material is formed to completely surround the four sidesurfaces 131 and the upper end of the luminous element 130 to blocklight emission from the four side surfaces 131 of the luminous element130. In this example, it is preferable that the coating layer 150 isformed with a height to the extent that the coating layer 150 does notcover an upper surface 133 of the luminous element so that light can beemitted only from the upper surface 133 of the luminous element 130 asillustrated in FIG. 4.

The coating layer 150 is coated between the respective luminous elements130 that are arranged substantially in the form of a matrix, and iscoated on an edge 111 of the printed circuit board 110 to surround therespective side surfaces (here, side surfaces indicate those that aredirected toward the edge 111 of the printed circuit board 110) of theluminous elements 130 that are arranged at an outermost portion of thedisplay module 100. Accordingly, by blocking light which is emitted fromthe luminous element 130 arranged at the outermost portion of each ofdisplay modules 100 arranged adjacent to each other through the opaquecoating layer 150, it is possible to basically prevent occurrence ofwhite seam.

Referring to FIG. 3, the coating layer 150 is filled in not only thefour side surfaces 131 of the luminous elements 130 but also in a spaceformed between the one surface 110 a of the printed circuit board 110and the respective luminous elements 150. In this example, since theanode electrodes 135 and the cathode electrodes 137 of the respectiveluminous elements 130 are covered by the coating layer 150, they aremade waterproof and dustproof, and can be basically prevented fromand/or avoid coming in contact with conductive foreign substances. As aresult, the luminous elements and electrodes can be safely protectedagainst static electricity.

The coating layer 150 may be opaque and may be made of a non-conductivematerial. In this example, it is preferable that the coating layer 150also has elasticity. For example, the coating layer 150 may comprisesilicon, acrylic resin, or epoxy resin. In this example, it ispreferable that a coating solvent that is provided to form the coatinglayer 150 has viscosity in a range of about 1000 to 10000 p(poise), andmore preferably 2000 to 9000 p(poise) to prevent and/or reduce thepossibility of the coating solvent flowing down after being dischargedby a nozzle. The coating layer 150 may be dark colored, for example, maybe black, in order to effectively block light that is emitted from theside surfaces 131 of the luminous elements 130.

The coating layer 150 may be formed with a height h3 that is lower thanthe height (h1+h2) of the upper surface of the luminous element 133 soas not to cover the upper surface 133 of the luminous element 130, butis not limited thereto. The coating layer 150 may have any height so faras the side surface of the luminous element 130 can be hidden to theextent that the coating layer 150 can prevent the light emission fromthe side surfaces of the luminous element 130. For example, if thecoating solvent is discharged so that the height h3 of the coating layer150 becomes about 0.7 mm that is lower than the height (h1+h2) of theupper surface of the luminous element 133, it rises along the sidesurface 131 of the luminous element 130 to reach a boundary line betweenthe side surface 131 and the upper surface 133 of the luminous element130 by surface tension until the coating solvent is cured. Accordingly,the upper surface of the coating layer 150 may become a concave surfacehaving a predetermined curvature toward the one surface 110 a of theprinted circuit board 110. As described above, it is preferable that theheight h3 of the coating layer 150 is set to an appropriate height inconsideration of the height (h1+h2) of the upper surface of the luminouselement 133. In this example, the optimum condition for preventing thewhite seam is to form the coating layer 150 so that the coating layer150 completely covers the side surfaces of the luminous elements 130.However, in the actual manufacturing process, the soldering amountsformed between the patterns 115 and 117 of the printed circuit board 110and the electrodes 135 and 137 of the luminous elements 130 differ fromeach other, deviation occurs in the mount flatness of the luminouselements, and thus the printed circuit board 110 is minutely flexed inan SMT process that is performed at high temperature. Due to this, theheight of the luminous elements 130 that are mounted on the printedcircuit board 110, which is measured from the upper surface of theprinted circuit board 110 to the upper surfaces of the luminous elements130 may not be equally maintained, and in this example, the mountingerror may be about 1% to 5%. Due to the mounting error, the upper endportions of the side surfaces of the luminous elements 130 may not beminutely covered by the coating layer 150, but this may not cause thewhite seam.

FIG. 5 is a cross-sectional view of a part V as indicated in FIG. 1illustrating a state where edge portions of coating layers of adjacentdisplay modules come in contact with each other.

Referring to FIG. 5, if a gap g2 is formed between display modules 100that are adjacently arranged due to a manufacturing tolerance or thelike, an edge portion 151 may further include a projection portion 152and may be formed to project further than an edge 111 of the printedcircuit board 110 for a predetermined width w5 (see FIG. 3) so that thegap g2 can be hidden by the coating layer 150 of the display modules100. Accordingly, as seen from the front of the display module 100 asillustrated in FIG. 2, the outline of the coating layer 150 becomeswider than the outline of the printed circuit board 110, and thus theblack seam that may occur in the display device in the related art canbe basically blocked.

In this example, the projection portion 152 of the coating layer 150 maybe formed to further project only with respect to at least one of edges111 on four sides of the printed circuit board 110. For example, asillustrated in FIG. 1, when a plurality of display modules 100 arearranged in the form of a matrix, it is enough that the projectionportion 152 is formed only on the edge portion 151 of the coating layer150 that corresponds to sides of the display module, which comes incontact with another display module 100, in accordance with thepositions of the display modules 100.

Referring to FIG. 3, the projection portion 152 of the coating layer 150may be formed up to a predetermined height h4 from the one surface 110 aof the printed circuit board 110. In this example, it is preferable thatthe height of the projection portion 152 is lower than the height(h1+h2) of the upper surface of the luminous element 133.

The width w5 of the projection portion 152 of the coating layer 150 maybe smaller than the gap g2 between the printed circuit boards 110 of theadjacent display modules 100, and may be equal to or larger than ½ ofthe gap g2. The width w5 of the projection portion 152 of the coatinglayer 150 may be set in consideration of the dimensions that satisfy thecondition on which the gap g2 of the printed circuit boards 110 of theadjacent display modules 100 can be hidden by the projection portion152.

The projection portion 152 of the coating layer 150 may have a slantingsurface 153 that is slanting at a predetermined angle θ1 in a lateraldirection of the coating layer 150 from the edge portion 151 of thecoating layer 150. For example, the angle θ1 of the slanting surface 153may determine the width w5 of the projection portion 152, and may havevarious angle values, for example, in a range of about 15° or 30°. Theprojection portion 152 and the slanting surface 153 may be formed by ajig 200 (see FIGS. 7 and 8) that is arranged along the edges 111 of theprinted circuit boards 110 during a coating process. The jig 200 (seeFIGS. 7 and 8) may be used in the process of forming the coating layer150 on one surface 110 a of the printed circuit board 110, and the edgeportion 151 and the projection portion 152 of the coating layer 150 maybe formed by the jig 200.

Hereinafter, referring to FIGS. 6 to 12, an example process of forming acoating layer on a display module according to an example embodiment ofthe present disclosure will be described in greater detail.

FIG. 6 is a flowchart illustrating an example process of forming acoating layer on a display module according to an example embodiment ofthe present disclosure.

First, a display module 100 in which a plurality of luminous elementsare arranged at predetermined intervals on one surface 110 a of aprinted circuit board 110 is prepared (S1). Before forming the coatinglayer 150, the display module 100 is set on a prescribed die (notillustrated) to perform a coating process.

FIG. 7 is a plan view illustrating an example state where a jig is setalong edges of four sides of a printed circuit board before a coatinglayer is formed, and FIG. 8 is a cross-sectional view of a displaymodule and a jig taken along line VIII-VIII as indicated in FIG. 7.

Referring to FIGS. 7 and 8, a jig 200 is set to come in close contactwith edges 111 of four sides of a printed circuit board 110 (S2).

The height h7 of the jig 200 may be set to be equal to or higher thanthe height of the upper surface 133 of a luminous element 130. This isto prevent and/or avoid a coating solvent L that is discharged betweenthe luminous element 130 and the jig 200 from overflowing to an outside,and in this example, it is preferable to additionally consider thedischarge amount of the coating solvent L being discharged.

Further, in order to form a projection portion 152 of a coating layer150, a support surface 210 may be formed on the inside of the jig 200.The support surface 210 may be formed to be slanting at a predeterminedangle θ2 in an outward direction of the jig 200 in a direction from aprescribed position (i.e., height h8 as illustrated in FIG. 8) to anupward direction with respect to an inner surface of the jig 200. Inthis example, the slanting angle θ2 of the support surface 210 maydetermine the angle θ1 of the slanting surface 153 of the projectionportion 152.

FIG. 9 is a diagram illustrating an example discharge device fordischarging a coating solvent that is filled between respective luminouselements of a display module and between the outermost luminous elementand a jig, and FIGS. 10A and 10B are diagrams illustrating an exampleprocess of discharging a coating solvent through an operation of a piezovalve that is provided in an example discharge device.

As described above, if setting of a jig 200 is completed, a coatingsolvent L is spread onto one surface 110 a of a printed circuit board110 as a discharge device 300 for discharging the coating solvent L ismoved (S3).

If the setting of the jig 200 is completed, the coating solvent L issupplied from a coating solvent supply source (not illustrated) and istemporarily stored in a storage chamber 310 of the discharge device 300.The storage chamber 310 may include a nozzle 330 formed on the lowerside of the storage chamber 310 to discharge the coating solvent L, anda supply pipe 350 formed on one side of the storage chamber 310 tosupply the coating solvent L. In this example, it is preferable that thenozzle 330 has a diameter d in a range of 50 to 300 μm that is smallerthan the gap g1 so that the coating solvent L can be filled in a verynarrow gap g1 of 0.3 to 2 mm between the respective luminous elements130. The diameter d of the nozzle 330 is set in consideration of thecondition on which the upper surfaces of the luminous elements 130 arenot stained with the coating solvent L when the coating solvent L isdischarged. Further, the coating solvent L may have viscosity in a rangeof about 2000 to 9000 p(poise) to lower and/or control the speed atwhich the coating solvent L flows down from one surface 110 a of theprinted circuit board 110 (or to make the coating solvent L maintain itsshape to some extent) after being discharged by the nozzle 330.

Further, the discharge device 300 may be provided with a piezo valve (ormicro piezo valve) 370 provided on an upper side of the storage chamber310 to discharge a minute amount of the coating solvent L. If a power isapplied, the shape of the piezo valve 370 is alternately modified asillustrated in FIGS. 10A and 10B, and the piezo valve 370 discharges apredetermined amount of coating solvent L that is stored in the storagechamber 310 through the nozzle 330. For example, if the piezo valve 370is drawn to the inside of the storage chamber 310 as illustrated in FIG.10A, the coating solvent L that is stored in the storage chamber 310 ispressed, and a predetermined amount of the coating solvent L isdischarged through the nozzle 330. On the other hand, if the piezo valve370 projects to an outside of the storage chamber 310 as illustrated inFIG. 10B, the discharge operation of the coating solvent L that isstored in the storage chamber 310 is temporarily stopped.

The discharge device 300 discharges a prescribed amount of the coatingsolvent L as moving on X-axis and Y-axis between the respective luminouselements at a predetermined speed. In this example, it is preferablethat the discharge amount of the coating solvent L is set inconsideration of the extent that corresponds to the height h3 (see FIG.3) of a coating layer 150 to be formed, which can completely surroundthe side surfaces of the luminous elements 130.

As described above, in the process in which the coating solvent L isfilled between the respective luminous elements 130 and between theluminous elements positioned at the outermost portion and the jig 200,the coating solvent L covers between one surface 110 a of the printedcircuit board 110 and the bottom surfaces of the luminous elements 130,the anode electrodes 135 and the cathode electrodes 137 of the luminouselements 130, and the patterns 115 and 117 of the printed circuit board110 in all.

FIG. 11 is a diagram illustrating an example state where filling of acoating solvent between respective luminous elements of a display moduleand between the outermost luminous element and a jig is completed.

As illustrated in FIG. 11, if the coating solvent L is filled at apredetermined height, the coating solvent L is cured for a predeterminedtime in a state where the jig 200 maintains its setting state to formthe coating layer 150 (S4).

If the coating layer 150 is formed through curing of the coating solventL, the jig 200 is separated from the edges 111 of the printed circuitboards 110 (S5). A normal coating solvent has viscosity after beingcured, and thus it may be difficult to separate the jig 200 from thecoating layer 150. In order to address this problem, the surface of thejig 200 may be processed with a special material having a releaseproperty, for example, Teflon.

Thereafter, the slanting surface 153 that is provided on the projectionportion 152 of the coating layer 150 may be processed using a prescribedtool. For example, a cutting process may be performed to smooth theslanting surface 153 using a grinder (not illustrated). In this example,it is also possible to set the slanting angle of the slanting surface153 through the cutting process.

FIG. 12 is a diagram illustrating another example of a jig that guidesfilling of a coating solvent.

As described above, when a plurality of display modules 100 are arrangedin the form of a matrix, it is not necessary to form the projectionportion 152 on the edge portion 151 of the coating layer 150 on the sidethat does not come in contact with the adjacent display modules inaccordance with the positions of the display modules 100. Accordingly,in the case of forming the edge portion 151 having no projection portion152, another jig 230 of which the support surface 231 is not slantinglyformed as illustrated in FIG. 12 may be used. In this example, thesupport surface 231 of the other jig 230 may be formed to be positionedsubstantially on the same plane as the edge 111 of the printed circuitboard 110.

Accordingly, in this example embodiment, when the coating layer 150 isformed, a jig 200 having a slanting support surface 210 and another jig230 having a non-slanting support surface 231 may be variously used.

FIGS. 13A, 13B, 13C and 13D are cross-sectional diagrams illustratingvarious example cross-sectional shapes of an edge portion of a coatinglayer.

The coating layer 150 provided on the display module 100 may havediverse shapes in accordance with the shape (plane, curved surface, ormulti-stage bending surface) of the support surface 210 of the jig 200.

For example, referring to FIG. 13A, one side surface 153 a of theprojection portion 152 may be slantingly formed at a prescribed height,starting from the edge 111 of the printed circuit board 110.

Further, as illustrated in FIG. 13B, one side surface 153 b of theprojection portion 152 may be formed as a curved surface that is convexto an outside of the edge portion 151, or as illustrated in FIG. 13C,one side surface 153 c of the projection portion 152 may be formed to beconcave to the inside of the edge portion 151. Further, as illustratedin FIG. 13D, one side surface 153 d of the projection portion 152 mayhave a multi-stage bent surface.

On the other hand, the discharge device 300 used in this exampleembodiment is provided with the piezo valve (or micro piezo valve) 370for micro discharge control of the coating solvent L, but is not limitedthereto. It is also possible to use a pneumatic valve (not illustrated),or the like.

The foregoing example embodiments and advantages are merely examples andare not to be construed as limiting the present disclosure. The presentteaching can be readily applied to other types of apparatuses. Also, thedescription of the example embodiments of the present disclosure isintended to be illustrative, and not to limit the scope of the claims,and many alternatives, modifications, and variations will be apparent tothose skilled in the art.

What is claimed is:
 1. A display module comprising: a printed circuitboard; a plurality of luminous elements arranged on the printed circuitboard; and a coating layer disposed between each of the luminouselements, the coating disposed around side surfaces of each of theluminous elements and the coating also positioned at an outermostportion of the display module and formed to have a height that issubstantially equal to a height of the side surfaces of the luminouselements to block light emitted from side surfaces of each of theluminous elements.
 2. The display module as claimed in claim 1, whereina pitch between adjacent of the luminous elements is set to be in arange of 0.3 to 2 mm.
 3. The display module as claimed in claim 1,wherein a size of the luminous element is defined to width×length×heightand wherein a range of the width×length is 0.5 mm×0.5 mm to 3 mm×3 mm,and a range of the height is 0.5 mm to 1.2 mm.
 4. The display module asclaimed in claim 1, wherein the coating layer substantially coverselectrodes of each of the luminous elements.
 5. The display module asclaimed in claim 1, wherein the coating layer comprises an opaquenon-conductive material.
 6. The display module as claimed in claim 5,wherein the coating layer comprises silicon, acrylic resin, or epoxyresin.
 7. The display module as claimed in claim 1, wherein a viscosityof a coating solvent that forms the coating layer is in a range of 2000to 9000 p(poise).
 8. The display module as claimed in claim 1, whereinthe printed circuit board comprises a curved surface.
 9. A displaymodule comprising: a printed circuit board; a plurality of luminouselements mounted on the printed circuit board; and an opaque coatinglayer formed on the printed circuit board to surround side portions ofeach of the luminous elements, the opaque coating layer having an edgeportion that forms an outer portion of the opaque coating layer, and theedge portion having a projection portion that projects further than anedge of the printed circuit board.
 10. The display module as claimed inclaim 9, wherein the edge portion of the coating layer is configured tocontact an edge portion of a coating layer of another display modulethat is arranged adjacent to the display module.
 11. The display moduleas claimed in claim 10, wherein the coating layer has an elastic forcewherein the edge portions of adjacent coating layers contact each otherwithout forming a space therebetween.
 12. The display module as claimedin claim 9, wherein the edge portion of the coating layer projectsgradually slantingly in a direction away from the printed circuit board.13. The display module as claimed in claim 9, wherein the edge portionof the coating layer is slanted to form an acute angle with a virtualstraight line that vertically extends from the edge of the printedcircuit board.
 14. The display module as claimed in claim 9, wherein theedge portion of the coating layer has a planar or curved side surface.